#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int moths(int a)
{
	if (a <= 2)
	{
		return 1;
	}
	else
	{
		return moths(a - 1) + moths(a - 2);
	}
}


int main()
{
	int a;
	scanf("%d", &a);
	int b = moths(a);
	printf("%d", b);


	return 0;
}